The U.S. Secret Service, responsible for protecting the nation’s currency, has been pursuing them for nearly 70 years, through 13 Administrations and 12 different directors. The investigation has spanned three continents and involved some of the most famous coin collectors in the world, a confidential informant, a playboy king, and a sting operation at the Waldorf Astoria in Manhattan. It has inspired two novels, two nonfiction books, and a television documentary. And much of it has centered around a coin dealer, dead since 1990, whose shop is still open in South Philadelphia, run by his 82-year-old daughter.